The present invention relates to a blood pressure monitor, a calibrating device and system and a method for calibrating a wrist type blood pressure monitor.
It is well known to use electronic blood pressure monitors for measuring the blood pressure on a patient. Mainly in the field of blood pressure monitors for home it is also known to measure the pressure around the wrist of the patient. This is preferred because of the easier application of the pressure cuff around the wrist as compared to the upper arm.
With regard to the quality of the measurement, wrist type blood pressure monitors are, however, somewhat less favourable. Wrist type blood pressure monitors have always a higher interindividual scattering of the measurement accuracy. This is due to the sensitive and complicate anatomical situation on the human wrist. While in the wrist, there are two arteries, the ulnar and the radial artery, the upper arm comprises just one artery. Measurements on the upper arm are known since a long time and therefore have less uncertainties.
Known blood pressure monitors are calibrated for an anatomical situation which corresponds to an average patient. This calibration may not be adapted to patients having e.g. relatively small or large wrist in the case of wrist type monitors.
It is an object of the present invention to overcome the draw-backs of the prior art, especially to provide a wrist type blood pressure monitor which allows an optimum measurement of the blood pressure on the wrist also for patients who have a different anatomical situation as compared to the average patient. A further object of the invention consists in providing a calibration device for calibrating a wrist type blood pressure monitor. Still a further object of the invention consists in providing a system for calibrating a wrist type blood pressure monitor. An other object of the invention consists in providing a method for calibrating a wrist type blood pressure monitor. The blood pressure monitor shall be simple and economic to manufacture and easily to use and apply.
According to the present invention, these objects are solved with a blood pressure monitor, a calibrating device, a calibration system and a method for calibrating a wrist type blood pressure monitor having the features of the independent patent claims. Calibrating shall mean in the context of the application any adjustment or modification of data stored in a memory in the BPM and used for calculating the blood pressure values.
The blood pressure monitor according to the invention comprises in a known manner an inflatable cuff e.g. adapted to be placed around the wrist of a patient, a pressure sensor for measuring the pressure within the cuff and a calculating arrangement for calculating the blood pressure values based on pressure values measured within the cuff. Such blood pressure monitors are known to those skilled in the art. The blood pressure values, i.e. the systolic and the diastolic blood pressure are determined e.g. with the oscillometric method.
According to the present invention, the calculating arrangement comprises an editable memory for storing data such as calibration data to be used in the calculation process of the blood pressure values within the calculating arrangement. Modifiable data can also be the weight, age or other parameters of the user. In contrast to know blood pressure monitors, where calibration data are pre-set in the factory, the present invention allows to recalibrate the blood pressure monitor by editing the calibration data in the memory. If e.g. a user becomes aware of the fact, that measured values are continuously too high or too low, the blood pressure monitor can be recalibrated. Obviously, the present invention is also useable for calibrating others than wrist type blood pressure monitors, such as finger type monitors or also upper arm monitors, if a reasonable reference site is available.
In a preferred embodiment, the blood pressure monitor comprises an interface connector which is connectable to a calibration device. The calibration device especially may comprise an upper arm type blood pressure monitor. For calibrating the wrist type blood pressure monitor, the blood pressure is measured with the usually more accurate upper arm blood pressure monitor. Other reference measurement sites are also conceivable.
The wrist type blood pressure monitor can be connected to the calibration device via the interface connector. The calibration data on the editable memory can thereafter be adapted in accordance with the blood pressure values measured with the upper arm type blood pressure monitor.
In a further preferred embodiment, the blood pressure monitor comprises a battery compartment for batteries. The interface connector is preferably arranged within this battery compartment. The interface connector therefore is not visible to the user if the battery compartment is closed.
The interface connector is preferably adapted to be connected to an external power supply during calibration. The external power supply can be especially provided by the calibration device. For connecting the interface connector of the wrist type blood pressure monitor to the calibration device, the batteries must be removed first. As soon as the wrist type blood pressure monitor is connected to the calibration device, power for the wrist type blood pressure monitor is supplied by the calibration device.
The editable memory is preferably an EEPROM or a flash-RAM which can be arranged in addition to a memory on the chip of the monitor in which the factory values are stored.
The calibration device for calibrating a wrist type blood pressure monitor according to the present invention comprises a inflatable cuff adapted to be placed around the upper arm of a patient, a pressure sensor for measuring the pressure within the cuff and a calculating arrangement for calculating the blood pressure values based on the pressure measured within the cuff. According to the invention, the calculating arrangement comprises an interface connector connectable with a wrist type blood pressure monitor. Calibration information based on the measurement of the blood pressure made on the upper arm is transferred to the wrist type blood pressure monitor via the interface connector.
The calibrating device preferably comprises a power supply for the wrist type blood pressure monitor during calibration.
A system for calibrating a wrist type blood pressure monitor mainly comprises a calibration device and an upper arm blood measuring monitor. The calibration device is connected or connectable to the wrist type blood pressure monitor. Preferably, the calibration device and the upper arm blood measuring monitor form one unit.
The method for calibration a wrist type blood pressure monitor according to the invention comprises the following steps:
a) The blood pressure of a patient is measured with the wrist type blood pressure monitor to be calibrated.
b) Before or after step a), the blood pressure is measured with an upper arm blood pressure monitor.
c) The blood pressure values obtained in steps a) and b) are compared with each other, e.g. in a calibration device.
d) Depending on the result of the comparison of step c), the wrist type blood pressure monitor is recalibrated, if necessary.
Recalibration is preferably made automatically with the calibration device. It is also conceivable to make a manual recalibration based on values measured with the upper arm blood pressure monitor. In this case, it will be sufficient to enter the correct setting values into the wrist type blood pressure monitor before or after a measurement with the wrist type blood pressure monitor. In this case, it is not necessary to establish a physical connection between the upper armblood pressure monitor and the wrist type blood pressure monitor. The calibration device in this case is contained within the wrist type blood pressure monitor.
In a preferred embodiment of the method, steps a) and b) are repeated, e.g. three times. This enhances accuracy of the measurement and therefore of the calibration.
In a further preferred embodiment, before carrying out step c), it is verified if the blood pressure values measured in steps a) and/or b) are within a predetermined range. The range can be xc2x120 mmHg for the systolic blood pressure and xc2x112 mmHg for the diastolic blood pressure.
If the values are not within the predetermined range, steps a) and/or b) may be repeated once more.
In a further preferred embodiment a pause may be made between steps a) and b) and between repetitions of the measurements.
In a further preferred embodiment, the wrist type blood pressure monitor and the upper arm blood pressure monitor are coupled to each other with respective interface connectors before steps a) and b) are carried out. With such a connection, manual entry of data can be dispensed with.
In a further preferred embodiment, the power for the wrist type blood pressure monitor during calibration is supplied by the calibration device. It is necessary to edit the editable memory for calibration. This process can be rather energy consuming. It is therefore preferred, that during calibration, power is not supplied by batteries contained within the wrist type blood pressure monitor but by an external power supply.
The wrist type blood pressuring monitor according the invention is used by the owner in a known manner. If the owner wants to make sure, that his results correlate well with a reference site e.g. the upper arm results, the blood pressure monitor may be recalibrated. For this purpose, a doctor or the vendor of the blood pressure measuring device is provided with a calibrating device. The blood pressure on the upper arm can be measured under the control of a doctor or in a pharmacy. The wrist type blood pressure monitor is thereafter recalibrated. In most general terms, the present invention consists in recalibrating an electronic blood pressure monitor on behalf of blood pressure values determined in a reference measurement and in providing a blood pressure monitor therefore.